<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
          #test{
              display: flex;
              width: 300px;
          }
          .a{
              width: 300px;
              border: 1px solid red;
              flex: 0 0 auto;
          }
    </style>
</head>
<body>
<div id="test">
    <div class="a">111</div>
    <div class="a">111</div>
    <div class="a">111</div>
    <div class="a">111</div>
    <div class="a">111</div>
</div>
</body>
</html>